Shallow luminous fluorescent lighting fixture



Dec. 16, 1958 M. BODIAN ET AL 2,864,939

SHALL IOW LUMINOUS FLUORESCENT LIGHTING FIXTURE Filed April 22, 1957 2Sheets-Sheet 1 WKW Dec. 16, 1958 M. BODIAN ET AL SHALL-OW LUMINOUSFLUORESCENT LIGHTING FIXTURE 2 Sheets-Sheet 2 Filed April 22, 1957 mm Gnom mm ATTORNEY SHALLOW LUMINOUS FLUQRESCENI-LIGHTING.

Marcus Bodian, Los Angeles, and William B. Rosenfield,

Pacoima, Calif, assignoi-s to Sunbeam Lighting Company, Los Angeles,Calif.

ApplicationApril 22, 1957, Serial No, 654,3 67 Claims. (Cl. 240-5111)This invention relates to a luminous fluorescent lighting fixture.

One object of the invention is to provide a self-luminous enclosedceiling type light fixture of whichfs'ubstan tially the only portionvisible from the floor is an evenly" lighted translucent cover. Anotherobject is to provide a four lamp ceiling type fluorescent light fixturewith a translucent cover which is shallow and lies close to thereference being made to the accompanying drawings in which:

Fig. l is a perspective view of a fluorescent light fixture as mountedon a ceilingQfollowing'our invention;

Fig. 2 is a bottom plan view, with parts broken away to show portions ofthe interior structure; Fig. 3 is a fragmentary vertical cross-sectionalview taken on the line 33 of Fig. 2;

Fig. 4 is a vertical cross-sectional view taken on the line 44 of Fig.2, the essential elements intliis'drawing being proportionally scaled; iFig. 5 is a fragmentary vertical cross-sectional view taken on the line5-5 of Fig. 3;

Fig. 6 is a fragmentary plan view taken on the line I 6-6 of Fig. 5;

Fig. 7 is a perspective view of the intermediate V- shaped reflectorswhich are ata ched to the base plate of the fixture; and i Fig. 8 is aperspective view separately showing the ballast housing including itsV-shaped bottom reflecting surfaces. l

Referring to the drawings which show a preferred form of our invention,the fixture consists of a top plate 11 which is generally flat andadapted to be mounted parallel to and adjacent the ceiling, being spacedfrom the ceiling by the ballast housing cover 12 which is attached toup-turned margins 13 defining a longitudinal opening 14 in the center ofsaid top plate 11, this opening being.

adapted to receive the sides 15 of the ballast housing 16 (shownparticularly in Fig. 8). Pushed-out tabs 17 are provided on the innersurface of the up-tur'ned margins 13 of the opening 14 in the cover,these tabs being spaced and arranged to engage the tab openings 18 onthe sides 15 of the ballast housing 16 as shown. This arrangementpermits the removal of the ballast housing 16 when it is desired to getaccess to the ballast elements 19.

The ballast housing 16 consists of the said side walls 15, which areconnected by a pair of v-b'ottom 'plates 22 which are longitudinallyjoined at an external angle of about 226, the outer surfaces serving asreflecting surfaces for the light from the two inner fluorescent.larnps.

Air space for cooling of the ballast units 19 is provided on both sides,and underneath the units, in the space between the sloping reflectorplates.

The top plate 11 which is generally made of sheet metal and is longerthan it is wide is provided along the side margins with rectangulargrooves 20, each of these grooves 20 having an up-turned edge 21 which,in the preferred form shown, is level with the upper plane of the topplate 11. Attached to the under side of the top plate 11 and dependingtherefrom adjacent the ends of said plate are socket end members 23which are of sheet metal formed as structural beams to give strength andrigidity to the structure, these end members 23 being provided in theirupright portions with holes 24 in which are mounted electricalconnecting sockets 25 for the fluorescent lamps 26 which are used inthis fixture, these lamps extending from one socket end plate to theother.

A difluser frame 30 extending around the margins of the top plate 11 isremovably and hingedly mounted on said top plate 11, the diffuser frameholding a deeply dished translucent diffuser 31 which substantiallycompletely encloses-the fixture except the top plate, and which inclosed position is substantially the only portion of the fixturewhichisvisible from the floor beneath. The diffuser frame 30 consists ofstructural end members 32 which are shaped to cover the socket endmembers 23, and which have inwardly directed flanges 33 on their lowermargins. The frame 30 also comprises structural side members 34extending between the ends of said end members 32, being removably heldtogether by screw bolts 35. The side members 34 which are sheet metalstrips are edge-bent at the upper edge to a downwardly directed hingingedge 36 which'rests inside the grooves 24) in the top plate 11. The sidemembers 34 also have I inturned flanges 37 along their lower edgeportions.

The diffuser 31 consists of a molded or otherwise formed lighttransmitting sheet material dished to cover and enclose the fluorescenttubes, reflectors, etc. mounted on the top plate 11, the diffuser havingsloping walls 38 and outwardly turned edge flanges 39 extending from theupper edges of said walls, which flanges rest on the inturned flanges 37of the side members 34 and also on the inwardly directed flanges 33 onthe lower edges of the end members 32 of the diffuser frame 31 Thedished diffuser 31 is thus framed and supported by the diffuser frame 30so that when assembled, it serves as a unitary cover for the lightingfixture. When mounted in place, the hinging edges 36 of the diffuserframe rest in the grooves 20 on both sides of the top plate 11, theparts of the structure being proportioned so that the distance betweenthe up-turned edges 21 of the top plate is slightly greater than thedistance between the downwardly directed hinging edges 36 of thediffuser frame 30. When it is desired to gain access to the interior ofthe fixture, one hinging edge 36 of the frame 30 on one side only of thefixture is raised up and moved laterally until it clears the up-turnededge 21 of the groove 20, thus removing all support from one side of thediffuser frame 30 with the diffuser plate securely mounted therein. Theupturned edge 21 on the opposite side then cooperates with the hingingedge 36, also on the opposite side of the fixture, so that the frame 30and the mounted diffuser 31 are hingedly supported in a hanging downwardposition shown in broken lines in Fig. 4, giving full access to theinterior of the fixture. The diffuser frame 30 and the diffuser 31 areagain restored .to the closed position by raisingthe free hinging edge36 over the corresponding up-turned edge 21 of the groove-20 andallowing the hinging edge tothen restinside the groove. The displacementof the top plate 11 from the ceiling by the protrudingballast housing 16permits full opening of the diffuser frame 30 The difiuser 31 isgenerally flat on its under surface portion 40 between the sloping walls38 which have been described, except that preferably an invertedV-shaped boss or groove 41 is provided in the longitudinal directionPatented Dec. 16, 19 58 in the center of the flat portion 40, thisV-shaped groove on its inside surfaces being disposed to receiveincident light from the adjacent fluorescent lamps 26, as well as somereflected light from the Vreflector bottom of the ballast housing aswill be described. The central inverted V-shaped groove 41 in theditfuser 31 also serves to strengthen the diffuser 31, the diffuser 31being preferably made from a molded plastic material, a polyacrylicresin such as Plexiglas. The diffuser 31 is made translucent either bythe incorporation of opaqueing powders in the plastic composition orpreferably by minute etching of one or both surfaces of the Plexiglas,or by other suitable means. The depth of the dished diifuser ispreferably no greater than twice the diameter of the tubular fluorescentlamp 26.

Attached to the under side of the top plate 11 and disposed intermediatethe pairs of fluorescent lamps 26 on either side of the ballast housingare V-shaped reflectors which are arranged at angles tangential to thesurfaces of the lamps in order to reflect the light from the upperportions of the fluorescent lamps evenly over the inner face of thediffuser. The V-shaped reflectors 43 are preferably sheet metal, coatedor surfaced with a reflecting material such as Alzac, and are attachedto the top plate 11 by tabs 44.

he drawing, Fig. 4, shows, to proportional scale, the principaldimensions which are necessary to attain the shallow, fully enclosedfixture for four lamps, whose translucent cover or diffuser attains asubstantially uniform brightness over its entire area. The actualdimensions in cross-section are related to and based upon the diameterof the fluorescent lamps. One much used standard lamp has an outsidediameter of 1 /2 inches. Using a as a selected unit of length (forexample A; inch), a lamp diameter A is 12a; the distances between lampscenters, B and B, are 42 to 4811, and these centers are aligned parallelto the top plate 11; the minimum distance C of the diffuser 31 from thelamp surfaces is 8a; the total visible width of the diffuser is 93a; theV-shaped reflectors 43 have two reflecting faces 45, 45 which are 16a inwidth, and these faces are disposed at an external angle E of about 226to each other, intermediate the outer pairs of lamps; this angle makingthe reflecting surfaces parallel to the tangent to lamp surfaces; thebottom of the ballast housing has two reflecting surfaces 22, 22, whichare 18a in width, disposed in edge contact longitudinally at an exterior(to the housing) angle of about 226 to each other. The distance D fromthe base plate 11 to the flat portion of the diifuser is 29a. The lengthof the fixture is determined by the length of the available lamps; onestandard length being 48 inches.

When constructed in the essential proportions given above, using40Tl2/RS2500 Lu./4.l c./in. lamps (4), the diffuser, at the indicatedangles, had brightness values as follows:

The available light was directed 96 percent downwardly, and the over-allefficiency was 66 percent.

The advantages of our invention will be apparent from the abovedescription. By using reflectors to direct the light from the four lampson to the diffuser (which is also the enclosing cover for the fixture),a uniformly lighted luminaire is provided which is less in thicknessthan twice the diameter of the tubular lamps. The light is diffused touniform brightness which does not irritate the eyes. The fixture, eventhough spaced a little distance from the ceiling, to provide coolingair, still presents the shallow appearance simulating a recessed ceilingfixture. The unit fixtures as above described may be placed inmultiples, preferably in end-to-end relation, to give uniform roomlighting.

We claim:

1. A ceiling fluorescent light fixture comprising an elongatedrectangular ballast housing having a depending V-shaped bottom memberwith outer reflecting surfaces, the top of said housing being adaptedfor mounting against the ceiling; an elongated plane top plate for saidfixture, said top plate having a central elongated opening through whichsaid ballast housing extends and to which said top plate is attached forholding said top plate parallel to but spaced from the ceiling; a dishedtranslucent diffuser having a substantially plane face forming anenclosing housing for tubular fluorescent lamps, the end and sidemargins of said diffuser tapering upwardly toward the margins of saidtop plate; means at the side margins of said diffuser for removablyattaching said diffuser to the margins of said top plate; means foroper- 'atively mounting pairs of elongated fluorescent lamps inspaced-apart relation with the upper surfaces of said tubes closelyadjacent the under surface of said top plate, said pairs being disposedon both sides parallel to the reflecting surfaces of said ballasthousing bottom; and elongated V-shaped reflector attached to theunderside of said top plate and disposed intermediate the two lamps ofeach pair.

2. The ceiling fluorescent light fixture defined in claim 1, in whichthe means for mounting the diffuser to the margins of said top plateconsists of a turned-in-and-down strip on the side margins of saiddilfuser engaging a marginal trough on the side edges of said top plate.

3. The ceiling fluorescent light fixture defined in claim 1, in whichthe diffuser is provided with a centrally disposed longitudinallyinverted V-shaped rib whose apex is adjacent the apex of said V-shapedbottom member of said ballast housing, whereby the sides of saiddiffuserrib receive direct light from said fluorescent lamps whereby tomake said rib shadow free and of substantially equal brightness to theplane surface of said diffuser.

4. The structure defined in claim 1 in which the plain area of thediffuser is separated from the top plate by a distance not greater thantwice the diameter of the tubular fluorescent lamps.

5. In a fluorescent light fixture having a plane base plate adapted tobe mounted adjacent but spaced from a ceiling, and having a plurality offluorescent tubular lamps mounted in spaced-apart parallel relation onsaid base plate, and close to the surface thereof, and also having adished translucent diffuser underlaying and removably attached to saidtop plate to form a housing for said elongated fluorescent lamps; meansfor reflectively distributing the light from said fluorescent lampsevenly over the entire area of said dilfuser comprisingangularlydisposed plane reflecting surfaces attached to said base platedisposed intermediate and in light reflecting position adjacent pairs oflamps, said reflecting surfaces extending downwardly at least to theelevation of the axes of said lamp.

References Cited in the file of this patent UNITED STATES PATENTS

